Nanomaterials refer to solid materials consisting of superfine particles having a size of less than 100 nanometers. Because of their size effect, quantum effect, surface effect and interface effect, they have properties that are not possessed by traditional materials. With the rise of nanomaterials and the increasing maturity of their preparation method, it is found that nanomaterials have excellent friction properties. The use of nanoparticles as lubricating oil additives can make lubricating oil have the advantages of both fluid lubrication and solid lubrication, which can not only form an easy-to-shear thin film on the friction surface, but also fill and repair the friction surface to a certain degree, thereby producing a good lubrication effect.
There have been a lot of reports in the prior art about the application of inorganic nanoparticles in the field of lubricants. For example, CN1150958A discloses a polymer composite consisting of high-temperature resistant thermoplastic polymer and nanoparticles, which is filled and reinforced by the high-temperature resistant wear-resistant and self-lubricating low-density nanoparticle, wherein the nanoparticles include nano-siliconnitride, nano-siliconcarbide and nano-silica. The product has excellent self-lubricating properties. CN1301319C discloses a lubricating oil composition comprising silica nanoparticles, which is an extreme-pressure, anti-wear lubricating oil composition having excellent properties. In this invention the blend of base oil and nano-silica are added with the dispersing aid and synergist to achieve the dispersion of silica nanoparticles. CN1180079A and CN1354056A respectively disclose use of fatty acid modified metal oxide or hydroxide nano-fine powder and thiophosphate organic compound modified metal copper nanoparticles in lubricating oil field. CN1827753A discloses a fluorine-containing rare earth lubricating oil nano additive and preparation method thereof, the additive comprising base oil and rare earth fluoride nanoparticles coated with nitrogen-containing organic compound. CN101058760A discloses nano ceramic lubricating oil and preparation method thereof, the lubricating oil comprising conventional lubricating oil ingredients and being added with modified ceramic nanoparticles. It belongs to the field of preparation of lubricating oil medium for machinery operating, and is in particular applicable to lubricating oil and preparation method thereof used in automotive industry. In this invention, a stably dispersed concentrate of ceramic nanoparticles is successfully prepared by pre-dispersion method, and then a nano ceramic engine oil comprising nano ceramic particles in a weight percentage of 0.00001% to 5% is prepared. CN101235337B discloses a lubricant composition applicable to a sliding section or sliding member of an automotive internal combustion engine or power transmission apparatus to significantly lower friction coefficient, which comprises a lubricating base oil, an oxygen-containing organic compound, diamond nanoparticles and a dispersant for the diamond nanoparticles. CN101555430A discloses a lubricating oil composition comprising a base oil stock and carbon nanosphere dispersed therein, wherein the carbon nanosphere is surface grafted with alkyl group and is of hollow structure or filled with metals, metal alloys, metal oxides, metal carbides, metal sulfides, metal nitrides or metal borides.
Furthermore, in addition to inorganic nanoparticles, there are also some reports about the use of organic particulate gel in the field of lubricant. For example, the patents CN1856527A, CN1840622A and CN1861673A, as filed by Rhein Chemie Rheinau Co., Ltd., disclose microgel in non-crosslinkable organic medium and use of crosslinked microgel for improving temperature dependence property of non-crosslinkable organic medium. The dispersed phase of the lubricant composition in these applications is microgels prepared by means of chemical crosslinking with a polyfunctional compound or a peroxide. Although the lubricant composition containing the microgels can reduce the friction coefficient of the organic medium to a certain extent, the viscosity of the lubricant composition has poor viscosity-temperature relationship, as means that the viscosity increases dramatically with descending temperature and reduces rapidly with ascending temperature. The disproportional high viscosity at low temperature or disproportional low viscosity at high temperature may limit the use of the lubricant composition. Therefore, it is urgent to develop a lubricant composition featured with good viscosity-temperature relationship.